1. Field of the Invention
The present invention relates to forming a plurality of nanotubes having selective properties, and devices or systems including same. Particularly, the present invention relates to nanotube structures and methods of manufacture thereof. Further, the present invention relates to semiconductor structures and systems including nanotube structures, and methods of manufacture thereof.
2. Background of Related Art
Several efforts have been made to form nanotubes into patterned configurations (e.g., arrays), however the resulting arrays typically include several nanotubes exhibiting irregular spacing or having varying heights. Other efforts have shown that the growth of aligned nanotubes in several directions can be controlled in a single process. Though the functional feasibility to integrate nanostructures into micro-devices has been postulated, process couplings and scale mismatches between nano- and micro-fabrication processes limit the practical production of integrated devices. It has been recognized that growing a uniform length nanotube array would be extremely difficult.
There have been few efforts regarding the handling and manufacturing of carbon nanotubes. One group has worked on the directed assembly of one-dimensional nanostructures into functional networks by fluidic assembly with a surface-patterning technique. Another research group developed a method of assembling single-walled CNTs into long ribbons and fibers. In this method the nanotubes are dispersed in a surfactant solution and then the nanotubes are condensed in the flow of a polymeric solution to form a long ribbon. Companies are selling commercial quantities of nanotubes in the form of soot, which cannot be handled effectively during the subsequent manufacturing processes. Other companies are working on flat-panel displays using carbon nanotubes as emission tips. None of these companies have reported commercially viable manufacturing solutions for the mass production of nanotubes.
One method of forming a carbon nanotube comprises taking a sheet of graphite and reducing the size of the sheet such that the sheet becomes an extremely narrow strip of material. At a width of approximately 30 nanometers, the strip curls about a lengthwise axis and the opposing carbon bonds at the side edges of the strip join to form a tube approximately 10 nanometers in diameter. Thinner tubes having a diameter of between 10 nanometers and 5 nanometers can be formed in the same manner. It is also possible to produce multi-walled carbon nanotubes by curving a number of sheets of graphite (typically three to eight sheets) in a similar manner as forming a single wall carbon nanotube.
Generally, nanotubes may also be prepared by laser vaporization of a carbon target in a furnace at approximately 1200° C. A cobalt-nickel catalyst may facilitate the growth of the nanotubes because the catalyst prevents the ends of the CNTs from being “capped” during synthesis, and about 70% to 90% of the carbon target can be converted to single-walled nanotubes. While multi-wall carbon nanotubes do not need a catalyst for growth, single-walled nanotubes are preferably grown with a catalyst. Alternatively, a carbon-arc method to grow arrays of SWNTs has also been developed. In this method, ordered nanotubes are produced from ionized carbon plasma, and Joule heating from the discharge generated the plasma.
WO Patent 2004/033370 discloses method for making packets of nanostructures. More specifically, the method includes etching trenches in a silicon substrate, growing nanostructures therein. Further, the trenches are then filled with a filler material and any filler and/or nanostructure material extending beyond the trench is removed. The silicon substrate is etched away, resulting in a nanopellet surrounding the nanostructures and wherein each of the nanostructures has a generally uniform length and direction. However, such a method appears relatively limited in scope and applicability. Accordingly, improved methods for forming nanostructures and devices including same would be beneficial.